1. Field of the invention
This invention relates to slurries used in blast cleaning, honing, vibratory finishing, and machining and more particularly to a system and apparatus for separating unwanted fine particles from liquid suspended particulate solids.
Wet media blast apparatus is used for deburring, abrading smoothing or surface coating of manufactured parts accomplished by a stream of high velocity liquid containing hard particles. These hard particles are generally referred to in the trade as "grit".
The blasting apparatus utilizes high pressure liquid jets to drive the grit against the surfaces being treated and for washing way residual grit from the parts and the apparatus.
It is necessary to separate excess liquid before reusing the grit and since this blasting treatment with grit removes and scraps off, from the treated part, small pieces, particles of metal, mold, core sands, dirt and so forth, such contaminates are in the liquid and hard core particles which drain from the blasting chamber.
Returning liquid containing the blasting grit also contains oils, colloidal particles, detergents, surface coating material of various kinds which are washed away in the drainback of the wet media.
Such contaminates complicate the separation problem since some of the contaminates have floatation effects which tend to carry oil in foam with valuable grit which desired for reuse.
Accordingly it is desirable that the wet media be collected as it falls from the article being treated for reconditioning and returning to the blasting pump which is accomplished by this invention.
2. Description of the prior art
Typical blasting operations are one hopper slurry systems that do not attempt to remove the spent media and contaminates. The liquid and media are agitated to avoid clogging the pumps and lines with excessive concentrations of media. On account of the required agitation, floatable contamination, such as oil, remains in the solution and can recoat the work. Only low concentrations are used because of inconsistent agitation and start up clogging problems. As a result of not separating spent media from the slurry, the finish produced on the workpiece is different at the beginning and at the end of a run. When a build up of fines becomes unbearable, the mixture is dumped. Low grit concentrations greatly extend the time for finishing. Under these conditions, finished consistency is impossible.
U.S. Pat. No. 4,250,024 discloses a blast bead separator in a blasting apparatus which continuously separates the broken and undesired beads from the reusable beads. This is accomplished by used slurry being withdrawn from a hopper at the bottom of the blasting cabinet, pumped to the top of the separator apparatus, consisting of screen of selected mesh, which delivers the reusable whole glass beads to a bin while the remainder or unused undesirable particles pass downward to another, finer screen, retaining all but the liquid slurry medium. The slurry medium or water passes to a holding tank which is returned to the reusable glass beads by a pump.
Most washers currently recycle the grit unintentionally for the reason their systems do not incorporate a means of grit removal. All washers utilize a flat bottom tank with a pump intake slightly off the tank bottom, when sludge builds up to the pump intake, pump performance is reduced and the unit is shut down to be cleaned out.
Most systems utilize a coarse screen to avoid plugging spray nozzles or damaging the pump.
U.S. Pat. No. 4,213,475 discloses using washed off soils to improve workpiece washing or cleaning operations in which dirt is collected and reused.
This invention is distinctive over the above and other patents by concentrating the usable grit in the bottom of the hopper where it can be regulated for a desired concentration in the liquid and return to the cleaning area so that the fines may be removed and not take up the space of larger effective cleaning grit.